Overview of in-bore pipe cutting and welding tools for the maintenance of CFETR and EU-DEMO

Abstract

In the remote maintenance of fusion nuclear devices, one of the most challenging tasks is the cutting and the re-welding of large pipes that feed the breeding blanket. The narrow space around some of the pipes hinders the suitability of conventional orbital processes. For such pipes, both the cutting system and the welding one have to be compact enough to move along their interior, lock against the pipe inner wall and keep the position during the operation. The inner diameter and thickness of the pipes together with the other severe requirements related to the remote maintenance drive the choice of the processing technologies and the design of the tooling configuration. In this work, activities carried out by a joint team from EU-DEMO and CFETR on the in-bore cutting and welding operations are presented and discussed. For the in-bore cutting system a solution for the simultaneous parting and bevelling has been developed opting for a mechanical cutting with a pair of symmetrically distributed knives. A preliminary dimensioning of the motors has been made assuming the radial feed and the cutting speed of the knives. For the in-bore welding system, the TIG welding with filler wire has been considered as the most reliable and suitable technology within prescribed requirements and constraints. A multi-pass welding operation has been assumed. A conceptual design of both tools has been developed. The space constraint remains the most critical issue. Further verification and validation work is planned in close collaboration between European laboratories and the Comprehensive Research fAcility for Fusion Technology (CRAFT) at ASIPP in Hefei.